Wireless communications, in particular cellular communications, are an increasingly important part of daily life, and users of wireless communication devices expect fast and flawless transmission of information. Reducing the latency between transmissions is therefore desirable. A large bottleneck in the latency of wireless communications is retransmission of data in the event that a transmission fails due to interference in the physical channel.
In conventional systems, a base stations and user equipments (UEs), upon receipt of data from a transmitting device, send in return an Acknowledged (ACK) or Not Acknowledged (NACK) signal to let the transmitting device know whether the data was received successfully or not. If the transmitting device receives an ACK, it proceeds to transmit new data. If it receives a NACK, it must retransmit the data until the receiving device successfully receives the data. However, it takes time for a device to process the ACK/NACK signal, which introduces latency into the retransmission process. In some of these systems, the base station or UE is given multiple transmission time intervals (TTIs) to decode a received ACK/NACK signal and discover whether it needs to retransmit the previous TTI's data. It is therefore desirable to reduce this latency, and is ideal to retransmit data in the TTI immediately following receipt of a NACK signal.